Antioxidant and prooxidant activities of elderberry (Sambucus nigra) extract in low-density lipoprotein oxidation

Spray-dried elderberry juice, containing high amounts of anthocyanin glucosides, was investigated for its antioxidant and prooxidant potentials and mechanisms. A strong, concentration-dependent prolongation of the lag phase of copper-induced oxidation of human low-density lipoprotein (LDL) was found, but the maximum oxidation rate was unchanged. Peroxyl-radical-driven LDL oxidation showed both prolongation of lag time and reduction of maximum oxidation rate. In the case of copper-mediated oxidation, the anthocyanins were able to reduce alpha-tocopheroxyl radical to alpha-tocopherol. Clear prooxidant activity in copper-mediated oxidation was observed, depending on the time of addition of extract: whenever the extract was present from the beginning or added within the first 10 min; the antioxidant effect prevailed. Addition at later times led to a considerable reduction of lag phase and increase of maximum oxidation rate. No such effect was found in peroxyl-radical-mediated LDL oxidation; on the contrary, the extract was even able to-reduce the propagation rate considerably.